The present invention relates to a supporting mechanism for a movable member of linear pulse motors which are suitably used as motors for feeding heads of electronic printers, electric typewriters, floppy disc drives, etc.
As is well known, the linear pulse motor moves the primary magnetic flux generating unit or the secondary scale in a stepwise manner according to pulse signals supplied to the primary unit. A typical example of the prior art linear pulse motor of permanent magnet type is illustrated in FIG. 1A and B, in which the reference numeral 10 indicates a secondary scale in the upper face of which a comb-shaped toothed portion 12 is centrally and longitudinally formed. A guide rail 14 is attached to each lateral periphery of the upper face of the scale 10 adjacent to the toothed portion 12. Disposed above the upper face of this scale 10 is a primary magnetic flux generating unit 16, which is composed of iron cores or magnetic cores 18 and 20, side plates 22 and 24 for securing these cores 18 and 20 from their opposite sides, permanent magnets 26 and 28 magnetically coupled to the upper faces of the magnetic cores 18 and 20, coils 30-33 respectively wound around the magnetic poles 18A, 18B, 20A and 20B of the magnetic cores 18 and 20, and two pairs of rolling-contact bearings 38, for example, ball bearings, attached to the lower ends of the side plates 22 and 24 through shafts 40 and 40. When a predetermined pulse signals are supplied to the coils 30-33 the primary unit 16 stepwisely travels over the scale 10 by generating magnetic fluxes through the gap G between the magnetic poles 18A, 18B, 20A and 20B and the toothed portion 12. The scale 10 may be moved by fixing the magnetic flux generating unit 16.
Linear pulse motors are widely used in electronic printers and electric typewriters for feeding their heads which require functions of linear traveling and positioning. Recently there has arisen a strong need for reduction in dimensions and cost of the linear pulse motor as the printer and the electric printer are being reduced in volume and cost. In addition to these requirements reduction in thickness is required for the pulse motor used for feeding the head of the floppy disc drive.
As a result of study of these requirements of the linear pulse motor, we have found that the supporting mechanism using rolling-contact bearings places considerable limitations to the reduction in volume and thickness thereof. Furthermore, there is a general tendency that the reduction of the rolling-contact bearing in dimensions raises the cost thereof.